Air column resonance sound in circumferential grooves formed in tire treads is generated by means of resonance in a tube (air column) formed by the circumferential groove and the road surface, and the resonant frequency depends on the length of the air column formed between the circumferential groove and the road surface.
This air column resonance sound manifests itself in the form of noise inside and outside the vehicle, and its peak is often at around 1 kHz, which readily reaches the human ear. As a technique for reducing the air column resonance noise of circumferential grooves it is known to reduce the air column resonance noise by interrupting the flow of air in the direction in which the circumferential groove is formed, by providing so-called groove fences, in other words protrusions, which extend from the bottom or the walls of the circumferential groove, blocking all or most of the circumferential groove. However, interrupting the flow of air in the direction in which the circumferential groove is formed also interrupts the flow within the circumferential groove of water that penetrates into the circumferential groove when being driven on a wet road surface, and because there is a deterioration in the drainage of water interposed between the pneumatic tire and the road surface, handling stability on wet road surfaces deteriorates.
FIG. 4 of Patent literature article 1 discloses a technique aimed at achieving both drainage and a reduction in air column resonance sound by disposing within a circumferential groove three groove fences spaced apart from each other and extending respectively from the groove bottom and from opposing groove walls within the groove.
Also, FIG. 3 of Patent literature article 2 discloses a technique aimed at achieving both drainage and a reduction in air column resonance sound by disposing groove fences, which extend from the bottom of a circumferential groove, in such a way that the greater part thereof from the opening of the circumferential groove does not touch the groove walls.